I walk and suddenly it darkened sharply in my eyes, began to hold on to the door and then fell. I didn't even understand how I fell, what could it be?

Dizziness in healthy people usually happens from 2 things:

1. The brain receives too much oxygen: breathing often-often
2. The brain receives too little oxygen: could hardly breathe; with low blood pressure (hypotension, or its varieties - orthostatic hypotension ). Do you know your numbers? 120/80 should be.
3. You can also faint from:

• hunger;
• from severe physical or mental stress;
• from pills (there are some, from side effects it is impossible to get out of bed, and you cannot not drink them);
• from a sharp change in body position from horizontal to vertical position (this, by the way, can happen if the orthostatic reflex responsible for leveling blood pressure is triggered with a delay);
• mmm, here a familiar endocrinologist suggests that because of problems with the thyroid gland, you can slide down the wall at the most inopportune moment;

If you have such attacks of dizziness at least once a week, then it is better to overdo it and go to the doctor than to miss and, at best, go to the doctor :)

Health you!